


lovely bitter water

by hesperides



Category: Ensemble Stars! (Video Game)
Genre: Dubious Consent, M/M, Other, Overstimulation, Praise Kink, Tentacle Monsters
Language: English
Status: Completed
Published: 2020-02-06
Updated: 2020-02-06
Packaged: 2021-02-27 19:14:28
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings, Underage
Chapters: 1
Words: 4,979
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22580830
Author URL: https://archiveofourown.org/users/hesperides/pseuds/hesperides
Summary: It must be nice to live without a brain or nervous system, he thinks, surviving on nothing but the most basic responses to outside stimuli.
Relationships: Sakasaki Natsume/Shinkai Kanata
Comments: 16
Kudos: 91





	lovely bitter water

Natsume is disappointed, but not surprised, to find the marine biology club room empty when he enters it.

Kanata had promised to be there after classes ended for the day, assuring him with ever present smile and gentle pat on the head that he surely wouldn’t be late this time. Given his track record, Natsume took his word with a grain of salt, and the lack of any human movement in the spacious room confirms his unkind assumptions. Natsume has the sneaking suspicion that Kanata’s never been on time to a meeting or appointment in his life, and has no reason to believe he’s about to change that any time soon.

With a small sigh, Natsume sets his bag down by the door, inhaling the smell of salt and carefully balanced chemical treatments as he starts a winding circuit around the room. The soft blue light from the tanks casts everything in an alien glow that makes the otherwise nondescript space look like something from far away, more fantastic world. That’s the kind of scene he wants to cast over Switch’s next live, something that will sweep the audience off their feet and whisk them away to a dream. It’s a feat that’s achievable, tantalizingly close to being realized with the formulas Natsume’s drawn up and perfected over the last few days— given that Kanata shows up and delivers the chemicals Natsume needs.

He slow to halt in front of the towering jellyfish tank, leaning in towards the glass to get a better look at the cloudy puffs of soft tissue that float up and down on the artificially created currents inside. It must be nice to live without a brain or nervous system, he thinks, surviving on nothing but the most basic responses to outside stimuli. 

His eyes wander from each meandering dome to the next, a curious nagging in the back of his head telling him that there’s been a change since the last time he peered in on them like this. It’s the same four fish as always, the pale, saucer sized moon jellies that resemble the shape of Kanata’s hair in a way that Natsume doubts is wholly coincidental. His mouth purses, the sense that he’s missing something growing until it weighs down on his mind. He draws back, counting the tank occupants again before he realizes what’s different.

Behind the cylindrical tank, set up against the far wall of a clubroom, is a long black box. Or at least, that’s Natsume’s first impression, skewed through the curving glass and water of the tank he sees it through. When he steps around to get a clear view of it, he realizes his mistake. It’s another tank, larger than any other that Kanata has on display, and filled with black water that seems to be constantly moving in opposing currents. In scope, it’s closer to setups he’s seen in proper aquariums. How Kanata even got the thing inside the school is a wonder unto itself, and Natsume finds his feet moving on their own, rounding the jellyfish tank and approaching the new one.

Kanata’s warned him before about some of the new specimens he gets in, often cases of charity that have been shoved off on him by owners who could no longer care for their pets. Some of the animals could be ‘dangerous’, as Kanata put it, upset by their sudden change in situation. What harm they could do from the confines of a glass box, Natsume couldn’t guess, and he can muster little to no trepidation as he approaches the massive new tank, placed where it is unceremoniously on the floor.

Crouching down to get a better look at the strange water inside, he notes that rather than a proper lid, the thing’s been covered in multipurpose tarp, like the kind used by outdoorsmen. Natsume can only guess the thing hadn’t come with the lid, but Kanata had needed to cover it for some reason. Perhaps he was cultivating something in the strange water that couldn’t do with excess exposure? Kneeling down, he tries to get a better look at what’s inside, watching with piqued interest as he sees oil slick colors emerge from the moving mass of darkness inside, flashes of rainbow that catch the low lighting of the room. Natsume instantly finds his mind wandering to what sort of filtration has been arranged for the set up, with the way the water moves as though it has a life of its own.

It’s fascinating, almost mesmerizing to watch the pitch black water swirl around, to the point that it takes him more than a few seconds to notice the sensation of something wet dripping onto his head. Natsume’s hand immediately goes to touch his now damp hair, mind jumping to the logical conclusion of a leak in the ceiling above him, a plausible idea that he’s disappointed to discard the moment he looks up.

Sticking out from under the tarp, hovering just a few inches above him, is something thin, delicately tapered at the tip, and the same color as the water in the tank. Natsume has to blink a few times, his brain not processing what he’s seeing, and the correct word only comes from him when a water droplet, hanging low on the thing’s underside, detaches and falls into his hair again.

Tentacle. That’s the word he’s looking for. It looks similar to the ones he’s seen on octopus or squid, but without the line of suction cups running along the length of it. He chances a glance back down to the tank, trying to see if he can make out the familiar shape of one of those aforementioned creatures. Another tiny splash of water hits his him, pulling his gaze back up before he can try to ascertain any shapes moving in the murky depths of the tank and—

It’s moving. The little tentacle is creeping down, and Natsume finds himself frozen to the spot, watching in fascination as it wiggles down, coming closer and closer to his face. The spell is broken when its damp, startlingly smooth tip gently glances against the side of Natsume’s nose, sending him scuttling back and away from the tank, watching with disbelief as it follows him.

“No, you need to get back inside, Kanata-niisan will get upset if you make a mess,” he hisses under his breath, apparently not above speaking to marine life as though it can understand him. 

Perhaps it’s telling that his first concern is the trail of water it leaves as it slithers further out from beneath the covering, and not what possible contact with the creature could mean for him. He doesn’t have time to second guess his decision to try and herd the thing back into the water, sitting up on his knees and holding his palms up, pushing gently back in its general direction to … spook it, or something. Can it see him? Has it realized that it touched another living creature? Natsume is beginning to realize how stupid he looks, but he shoves the feeling down. There’s no one around to see him, making any worries about the damage this might do to his image unfounded.

The sound of something rustling laminated polyethylene snaps Natsume back to reality. The single tentacle hasn’t retreated, or responded to his gentle attempt at redirecting it the way he hoped. It’s stayed stock still, waiting, as three more similar looking appendages of varying sizes emerge from beneath the tarp to join it, dripping more water onto the floor as they unfurl in Natsume’s direction. 

One of them  _ does _ have suction cups, he notes, a frivolous thought that makes him a moment too slow in reversing his advance toward the tank to escape making second contact with the creature.

The tentacle that glances against the side of his hand is slightly larger than the first, smooth all the way around with a tip that splits open and wriggles against his skin. It slides against his fingers with a sureness of movement that gives him the impression that it’s not afraid of him, and strikes him as more curious than anything— cephalopods are very ‘smart’, a voice in his head that sounds much like Kanata’s supplies.

“Maybe he can play with you later, but I don’t have the time,” Natsume mutters, torn on what to do next as the tentacle curls around his hand, its surface damp, silk smooth, and leaving a wet trail in its wake.

Nothing awful seems to have happened to it since being exposed to the open air, so maybe it’s fine, an ill placed spot of optimism in Natsume tries to suggest. The sudden downward snaking movement of the lone tentacle, wrapping around his wrist and pulling him forward with no small amount of force, dashes that hope in record time. Natsume jerks back out of pure animal instinct, his primitive lizard brain kicking into gear and telling him to get away from the thing  _ now _ , but the others tentacles that had been hovering motionless spring into action. They strike out like loaded coils, snapping around both of his wrists and yanking him forward with another sharp jerk, making him stumble and nearly fall forward onto his stomach.

Any concern Natsume had for the things own well-being has been cast aside. Water and some thick, viscous liquid that coats its skin is running off the tentacles and into the fabric of his jacket, rivulets snaking beneath his shirt and trickling down the length of his arms. He tries to yank back, break the things grip, but the muscle of the tentacles flex like iron cords and keep him stuck in place.

His mind races with other possible methods of escape. He could kick the tank itself to try and startle it, but if he broke the glass he could hurt himself (or the creature, he supposes, adding it in as an unkindly late afterthought). Making sound loud enough to startle it was another possibility, given that it can hear, but drawing attention from a random student passing by was unappealing to him for a number of reasons. 

“Stop,” he says, a touch louder than when he was muttering to himself before. 

His stomach flips as it responds immediately— by sending out another pair of tentacles to reach for him. 

They seem to be aiming for his face, which he angles away from, making them hit his jaw instead. If it bothers them, they make no show of it, snaking down along either side of his throat as though it was their intention from the beginning. There’s only the briefest of pauses once they reach the edge of his turtleneck. They lift from his skin, turning to each other as if to communicate, and then dive beneath the fabric in an eerie synchronized motion. 

The gasp Natsume makes as they slither against his bare skin seems much louder than any other noise he’s made. It’s like he’s only now realized how fast his own heart's beating as the twin tentacles slide down, from his neck to his collarbone, and then on to his chest. The ones wrapped around his wrists tighten, as if they can sense his latest intent to try and make an escape. The fabric of his shirt is starting to become thoroughly soaked, making it stick to his skin and amplify the movements of the tentacles moving beneath it. It feels claustrophobic, like he’s trapped in a second skin that’s been stretched over his first, cold and clinging to every line of his body.

Natsume is at a loss. His mounting panic combined with his disbelief of even getting into this situation in the first place paralyzes his overly analytical mind. It makes the steady progression of the slick appendages crawling down his skin that much more visceral, his body seeming more sensitive to every minute curl and slide of the tendrils than it should be. There’s a warmth on his cheeks that’s spreading down his neck that he wishes he could write off as embarrassment, a cloying shame from being caught and prodded like an unusual specimen that’s washed ashore. That’s all, nothing more, and he repeats that steady tattoo of a lie in his head until tentacle slides over his already erect nipple. He can’t help the next gasp that flies from his mouth, or the way his body seizes up, but he wishes he could. The creatures movements all stop for his next inhale, and a sense of terrible dread mounts as he can almost feel the keen, animal interest emanating from the tank in front of him.

The other tentacle that had been making its way down the center of his breast diverges, moving opposite from where its partner has paused, before in agonizing unison, both begin to wrap around the hardened nubs beneath his shirt. 

It’s too much, and the strangled cry that wrenches from Natsume’s throat is greeted by the tendrils at his wrists tightening in response, the creature now clearly intent on keeping him where he is for this. He has to bite the inside of his cheek to keep another noise from escaping as the tentacles deft tips roll over his nipples in perfect sync, pushing and prodding them until Natsume has to squeeze his legs together, more of that heat spreading down to his chest and going straight to his groin. 

The thing doesn’t relent, going as far as to wrap around tug at the raised tissue it seems so fascinated by, gentle at first then hard enough to draw an unhindered whine from him. So much for the idea that it can’t hear him— the moving tentacles cease their activity at the sound, as if they’ve achieved whatever it was they were seeking.

Then even more are emerging from out of the tank, and a new level of panic crashes over Natsume. He twists his body, trying to turn away from the tank and break the hold it has on its arms, but the thing easily overpowers him. It drags him back, his spine knocking against the glass as it pulls his wrists up and behind him until he can feel his hands hit the rim of the aquarium, more velvety tendrils reaching out of the water to dance and slip against his fingertips. 

He’s neatly trapped now, and there’s little else he can do as the other tentacles descend on him, moving over his clothes this time, trailing down his shoulders and chest to go straight for his waist. His pants are tightly cinched by his belt, as per usual, but that works as an ineffective deterrent. As simple as a sigh, the appendages seem to flatten themselves in order to slip neatly into the sliver of remaining space between cloth and skin, roaming with a fervor Natsume can only think of as excited as they run over his hardening cock beneath his underwear.

The feeling is different from before, and when he forces himself to look down at the obscene squirming going on inside of his clothing, Natsume verifies that several of the new tentacles have the ridge of suckers running across their length. The sensation is a world away all the times when he takes himself in hand early in the morning or late at night, or when he’s let someone else do it. The way they both glide over and gently pull at his skin is sending his nerves into overdrive, each exploratory slide and twist making his entire body shiver and convulse. 

He can barely muster any surprise when another set of tentacles slips down his back, sliding beneath his clothing and running down the seam of his ass. They aren’t large enough that it’s overwhelming, but he’s still so worked up that their cursatory glides against his entrance tease out more embarrassing noises he can’t quite swallow. 

When one slides inside, that whine turns into a sharp mewl, high and trembling and breathlessly repeated when another joins it. There’s been far too little time for him to adjust, and although the tips that have penetrated him are thin enough to move with relative ease, Natsume can feel wetness gathering along his lashes as they push in further to explore him. 

The tentacles on his cock haven’t stopped their ministrations during this, some having found the places to curl beneath his underwear and touch him skin to skin. One winds around him, from base to head, so slow and purposeful that Natsume thinks that the creature has to know, at least in part, what it’s doing. There’s no way it can’t be responding to his noises, the strained twists of his body, the warmth bleeding through his wet clothing. He can tell himself that it’s impossible, everything about this is impossible, but it doesn’t make tentacles rubbing against the head of his cock or inner walls any less visceral or real.

His heart is pounding and he can’t suppress the sounds coming from his mouth anymore, the cry he makes when it pushes yet another tendril into him loud enough that he’s sure someone passing by in the hall could hear him. It’s steadily been pulling him back by his wrists, further and further, stretching his body out like it’s trying to pull more reactions from him, to wring him dry of all that he has.

When a tentacle wriggles up against his prostate, he believes that it can. Once he moans, shocked and deafening to his own ears, it just does it again, and again. The tentacles on his cock and nipples seem to move in time with it, bringing him to the edge without warning or mercy. He sees nothing but white as he squeezes his eyes closed, and before he knows what’s happening his orgasm is already on him, making him come in his already soaked pants with yet another mortifying whine. 

There’s no time to rest, no chance to come down, because they don’t show any signs of stopping what they’ve started. Now that they’ve found the reaction they’re looking for, they want  _ more _ , and Natsume’s legs kick out on their own as the tentacles continue to stretch him further open and writhe around his cock. He might be yelling now, or trying to, his voice becoming desperate and unrecognizable to him. He tells it to stop, begs it to stop, and he must tell it ‘no’ as well, since he hears it from somewhere nearby. His mind must be conjuring Kanata’s voice again, because it sounds like him, close enough that he might be standing over him, smelling of clean water and brushing his thumb against where the tentacles have him trussed at the wrists—

It’s enough to make him open his eyes, because Kanata  _ is _ there, crouched over him, green irises glowing like the phosphorescent jellyfish in the tanks around them. He’s staring intently, not at Natsume, but the thing behind him.

“No, no, he is not yours. You cannot behave however you want,” Kanata says, the emotion in his voice so rare that Natsume can’t imagine he’s heard it more than a handful of times. “You are a thankless ‘child’. I should have eaten you instead of listening to those people when they ‘begged’ for your life.”

Natsume is stunned into near silence as the tentacles begin to retreat, drawing back out from under his clothing, though he can’t help the pathetic little whimper he makes when ones nestled inside of him pull away, leaving him suddenly empty. Kanata’s fingers are touching the ones still encircling his upper arms, which refuse to budge, much to his clear displeasure.

“I don’t need to prove anything to you,” he says, haughty and demanding. “This one is ‘mine’. You are not allowed to touch him.”

There are little splashes as the bulk of the tentacles slip back into the water, cowed by Kanata’s strange and imperious behavior. It doesn’t strike Natsume as odd that he’s talking to it, Kanata does that all the time, but the tone he’s using, cool and sharp and making no effort to conceal his ire, isn’t one Natsume associates with his gentle ‘older brother’. Even with Eichi he manages a veneer of pleasantness to contain his malice. This is nothing but outright disdain.

Kanata’s mouth draws up into a pout, dissatisfied with whatever response he’s received. “It doesn’t matter that my ‘scent’ isn’t on him. You can’t mate with him.”

Natsume watches this all like it’s something far away, a play he’s seeing from nosebleed seats through binoculars. Kanata hasn’t moved or taken his hand off him, eyes fixed on the darkened tank with a fierce intensity he normally reserves for things like live performances or shattering a man’s skull. 

“I will put it back, and then I will toss you out on the ‘beach’. Some birds can tear you apart while you dry up in the sun.”

He starts when Kanata’s other hand goes to cup his face, the other boy’s eyes finally lowering to meet his own. All the cold edge vanishes in an instant, leaving only warmth of shallow summer waters that smile down at him.

“Nacchan, I told you not to ‘play’ with the fish here,” he scolds, using his thumb to wipe the tear tracks from his cheeks. “You could’ve been hurt, and I would’ve been very ‘angry’.”

“I didn’t— I didn’t do anything to it,” it’s a little strange how quickly brattish denial comes back to him, given the situation. 

Kanata tilts his head, indulging his immaturity with a familiar smile. “You are ‘all right’, but you should be more careful. Keep being a ‘good boy’ for me, Nacchan, won’t you?”

Natsume doesn’t react, can’t find the will to react, when Kanata sits up and begins undoing his belt. He pulls it free of its loops quick and business like, hooking his hands in Natsume’s pants and pulling them away with his underwear a moment later. He’s running so hot he barely notices the chill of the air on his bare skin, much more focused on Kanata putting his hands on both his knees, spreading his legs open so he can position himself in between them. His smile remains serene all the while, even as here pushes Natsume’s shirttails away to reach for his cock.

“Here, too?” he doesn’t stop with just pushing them aside, rucking his school shirt and turtle neck all the way up to expose his abused nipples. Natsume doesn’t know how to respond, blinking at Kanta dumbly and then not at all, eyes going wide when the other lowers his head to draw one into his mouth.

If Natsume says anything it’s not intelligent, a garbled mixture of words that comes out against the warmth of Kanata’s teeth and the drag of his tongue. He repeats the gesture with the opposite nipple, licking his lips when he pulls off it, making Natsume’s stomach flip with something that isn’t quite discomfort.

“Kanata-niisan?” Natsume watches, nothing more eloquent coming to him as Kanata palms at his cock, coaxing it to half hardness again. He hasn’t come down from the balcony seating yet, seeing this all as if he’s merely a spectator, but the stimulation so soon after his climax makes his body seize. Kanata gentles his touch after that, leaning in to nuzzle against the side of his neck, breathing in deeply.

“It’s ‘all right’. You don’t need to do anything else. Be a ‘good boy’ and I will take care of it.”

Natsume’s legs spread further open, without any direction from his mind when he feels Kanata’s fingers prodding at his rim. One slips in easily, making him squirm and moan, while Kanata’s brow furrows and his mouth presses into an unhappy line.

“You are very loose here … it wanted to ‘mate’ with you that badly,” he huffs, displeasure clear. “Nacchan ‘smells’ very sweet, but that’s no excuse.”

He doesn’t think Kanata’s talking about the oil he’s wearing today, but can’t imagine what else it could be. It’s difficult to hold onto any one thought right now, unable to follow the meandering lines that he weaves together to create the bigger picture he should be looking at. Easier to let Kanata tease him open with another finger, rather than consider the implications of what he’s doing.

The tentacles that hold his arms up haven’t withdrawn, keeping him from any attempts to move away, not that he wants to. Kanata’s hands are familiar, though it's not as if he’s touched him like this before, but he praises Natsume softly under his breath, tells him how ‘good’ and ‘cute’ he is, and Natsume can’t bring himself to mind it. He shifts his hips into Kanata’s hand when he strokes him, back and forth, and finds himself hanging on the other’s every word when he tells him to breathe in, then out.   
  
“In,” Kanata says, in his lilting sing-song. “And out.”

His fingers withdraw on the last word, stifling Natsume’s harassed sigh by sealing their mouths together. 

“In,” he repeats against Natsume’s lips, after the sound of less damp cloth rustling ends and a hand settles on his hip. 

Air fills Natsume’s lungs in the same breath that Kanata thrusts inside him, kissing him at the same time to swallow up reedy wail that rips from Natsume’s throat. It’s more solid and familiar than having the tentacles inside him, and there’s some comfort in that, but his body protests at the violation coming so soon after already being spent. It’s no help that Kanata doesn’t take any time to ease him into it either, burying himself to the hilt with one smooth motion. 

Kanata strokes a thumb over the sharp jut of Natsume’s hipbone, murmuring another ‘good boy’ that sends trails of fire crawling over his shoulders and down his back. He’s hard again, he realizes with belated surprise when Kanata gives his cock another squeeze. His eyes drift open, just wide enough to see the tableau of his own wet, glistening skin bared from chest to navel, and the precum beginning to dribble from the head his cock. Kanata’s hands on him look like polished ivory compared to the flush that’s spread over his body, holding Natsume in place as he shallowly rocks out of him. 

“Nacchan’s so ‘adorable’ like this,” he says, pushing back in with a heated sigh. “That’s why you need to be careful, or else something ‘bad’ might try to catch you and fill you up again.”

Natsume eyes fall shut and he nods blindly, his hips moving back and forth in staccato arcs with Kanata’s coaxing.

“If someone else found you, like Wataru,” Kanata croons, drawing back. “He would ‘tease’ you a lot more.”

The thought of Wataru seeing him how he is now, pulled apart and wrecked, sends the warmth from the base of Natsume’s spine pooling into his belly. He shakes his head, earning a soft giggle from the older boy. 

“I won’t tease you so much. Nacchan’s ‘company’ is enough for me.”

He might keep talking after that, but his thrusts become unforgiving and earnest, robbing Natsume of his last remaining scrap of will to listen to anything he says. His knees knock weakly into Kanata’s sides while he begins to set a steady rhythm, starting slow and speeding up in an impatient way that betrays Kanata’s excitement at having Nastume beneath him. 

Natsume lets him take the lead, and when the last of the tentacles retract their hold on him and retreat back to their tank, Natsume’s arms fall to Kanata’s shoulders, clinging onto him weakly. The sting of his overstimulated nerves has begun to fade away, bringing back sensations of pleasure that feel more natural and welcome than what was torn out of him before. 

He can tell when Kanata gets close, movements becoming less measured, the hand on his cock twisting around his length with an urgency that wasn’t there before. It’s more of that warmth when he spills over inside him, flooding Natsume with a complimentary heat that sends a shiver running through his body, from his head to his tightly curling toes.

Kanata keeps fucking him, angling his hips so the softening head of his cock brushes against that spot inside him, igniting fireworks behind his eyelids.

“I want to see it too, the face you make like this. Nacchan’s going to be a ‘good boy’ and show it to me.”

It’s not a question, and Nastume’s response overcomes him, his cock twitching and releasing in a wet mess all over Kanata’s fisted hand. When he tries to open his eyes his vision blurs, nothing but a muddied mess of green and blue swimming in his vision. The only sounds in the room are the gentle whirs of aquarium machinery and the labored breathing now coming from the both of them, the tank at Natsume’s back gone dead silent.

“Kanata-niisan,” he whines as one of Kanata’s arms wraps around his back, pulling him up into a sitting position that manages to lodge his cock even further inside Natsume. Kanata doesn’t respond at first, nudging at Natsume's cheek with his nose, like an animal scenting what it owns.

“See? He likes this better,” Kanata says against his skin, though Natsume can tell his words aren’t directed at him. “He ‘smells’ like he should, now that I’ve filled him all the way up.”

Natsume buries his face in the space between Kanata’s neck and shoulder when the other rolls his hips, too far gone to be ashamed of the broken moan it elicits from him. Kanata hums with gentle contentment, a sound meant to soothe while he moves his sticky hand around to stroke the place where they’re still connected.

“Not yours,” the cold snap is back in his voice again, stinging where Kanata whispers against his burning skin. “All mine.”

**Author's Note:**

> happy birthday my dearest son maybe one day i will write you getting railed in a situation where you get to be cool and sexy


End file.
